Hi,
I was feeling very virtuous that I ride my bicycle to work rather than
drive or go by train.
But then I thought that the train is probably more efficient than me
at converting energy to motion... so this might mean that I produce
more carbon-dioxide emissions from riding my bike than taking the
train.
I don't suppose it will change what I do... but can someone confirm
which method of transport is more environmentally friendy, with links
to relevant web-sites?
thanks,
Richard

Hi Richard,
What an interesting question!
How much energy the train expends converting energy to motion
really seems moot in this scenario, as the train is running whether
you are on it or not. The extra energy the train might expend if you
were on it is beyond the scope of this question! :-) However, the
number of people riding the train is surely varied day to day, so we
really don?t need to worry about the amount of energy needed if you
were on the train. The train is running daily, whether or not you are
aboard.
That said, if you are ON the train, and not putting off additional
CO2 from riding in a car, on a motorcycle or bicycle, you ARE ?saving?
CO2. Keep in mind you are putting off CO2 while ON the train too, but
a bit less and you are burning less energy sitting than pedalling a
bike.
Since this is not a true ?scientific? answer, I?ll go with the figure
I found on the link below- Humans exhale about 300 grams CO2 per
person per day
http://www.mrp3.com/bobf/global_warming.html
And this site:
PharmaciaRetirees put it in pounds: ?Humans exhale 2.2 pounds of CO2
per day or 803 pounds per year (over 1000 pounds per year for
joggers).?
http://www.pharmaciaretirees.com/environment.htm
For some reason British citizens give off more CO2, according to this
site. The site has some nice graphics on energy expended for walking,
biking, etc.:
http://www.skeltongrange.org.uk/transport.html
A motorcycle gives off about 0.3 pounds of CO2 per mile, in addition
to what you exhale while riding it!
So, in comparing a bicycle to a motorbike, with normal activities,
you?d exhale about 2.2 pounds a day, a bit higher if you go by
bicycle. If you rode a motorcycle just 10 miles, you are adding an
additional 3 pounds of CO2 to the environment.
Therefore, far less CO2 is produced if you ride a bike versus a
motorcycle. Now, since the average human exhales about 803 pounds of
CO2 per year, and a jogger puts off about 1000 pounds a year, let?s
put a bicycle rider at about 900 pounds a year. Riding a motorcycle
will add 900 pounds of CO2 after riding just 3,000 miles, in addition
to the 803 pounds a year you add just by being. Any motorcycle riding
will increase CO2 output.
A train/subway gives off about 0.6 pounds of CO2 per mile, while a bus
puts out about 0.7 pounds of CO2 per mile, according to the Delta Land
Trust site.
http://www.deltalandtrust.org/scorecard.html
You will add a bit less CO2 to the air by riding the train, since it
is running anyway. Riding a bicycle to and from the train station
instead of in a car, releases far fewer greenhouse gasses and you get
the health benefit of the exercise! A bicycle will add far less than a
motorcycle. All of these will add far less than a single passenger in
a car!
I don?t know if you were referring or a motorcycle or a bicycle in the
question. There are benefits to your health and wallet if you ride a
bicycle, especially if you DON?T ride along a busy highway, where you
will breathe in more pollutants like CO (Carbon monoxide).
Some useful sites:
==================
?Surprise! The answer to the first question is the bicycle. The
bicycle is the most efficient way to get around Walking, skate
boarding, roller blading or riding an animal takes more energy, in the
form of food, than peddling a bicycle. As noted in the graph below,
the next most efficient ways to get around are to share a ride with
others in a van, train, bus, or car. The most common way Americans get
around, however, is in a car or truck with only one person in it and
this is the least efficient and least environmentally sound way of
getting around, second only to the airplane.?
And
?Walking, biking, mass transit, and new car sharing options, NEVs,
e-bikes, and motorcycles could improve our quality of life, by slowing
down our pace and reducing road congestion and emissions from
transportation.?
http://www.nesea.org/greencarclub/funways.html
?A round trip of 1600 kms, (London to the South of France) by car with
the bike on the roof, creates 360 kg of CO2, the main greenhouse gas.
If you go by train and hire a bike when you arrive, you'll create 100
kg of CO2. If you go by plane, with your bike in the hold, you'll
generate a whopping 850 kg per person, which is more than the amount
produced by heating an average size house for a year! Estimates of the
contribution airplanes make to global warming are up to 15% and
rising. To arrest the acceleration of global warming it is accepted
that the West (that's you, my friend) must cut CO2 output by 80%.?
http://www.bristolcyclingcampaign.org.uk/grim/reaper31.htm
?Carbon monoxide (CO) -- A colorless, odorless, poisonous gas,
produced by incomplete burning of carbon-based fuels. including
gasoline, oil, and wood. Carbon monoxide is also produced from
incomplete combustion of many natural and synthetic products. For
instance, cigarette smoke contains carbon monoxide. When carbon
monoxide gets into the body, the carbon monoxide combines with
chemicals in the blood and prevents the blood from bringing oxygen to
cells, tissues, and organs. The body's parts need oxygen for energy,
so high-level exposures to carbon monoxide can cause serious health
effects. Massive exposures to CO can cause death. Symptoms of exposure
to carbon monoxide can include vision problems, reduced alertness, and
general reduction in mental and physical functions. Carbon monoxide
exposures are especially harmful to people with heart, lung, and
circulatory system diseases.?
http://www.smallbiz-enviroweb.org/compliance/glossary.htmlhttp://www.liftshare.org/download/car-passengers-analysis.pdf
?Carbon Dioxide (CO2) -- A colorless, odorless, gas that occurs
naturally in the earth's atmosphere. Significant quantities are also
emitted into the air by fossil fuel combustion. Emissions of CO2 have
been implicated with increasing the greenhouse effect.?
http://www.triangleair.org/glossary.htm
?Looking ahead, carbon dioxide emissions from transportation sources
in the United States are projected to grow at an average annual rate
of 1.8 percent between now and 2020. This compares to an overall
increase in CO2 emissions in the U.S. of 1.4 percent per year, meaning
emissions from transportation will become an even larger part of the
problem in the years ahead. This continuing growth will result from
projected increases in vehicle-miles traveled-translated, this means
more cars driving greater distances-as well as growth in freight
shipments and air travel.?
http://www.pewclimate.org/press_room/speech_transcripts/transcript_transport335.cfm
?Carbon dioxide (CO2) emissions from the consumption of gasoline,
diesel, and other fossil fuels are the principal cause of global
warming, which brings health and economic risks from climate change.?
http://www.greenercars.com/whybuy.htmlhttp://wwwistp.murdoch.edu.au/teaching/N212/n212content/topics/topic4/papers/sustranspt/sustranspt.html
Auto vs. Bike
http://www.kenkifer.com/bikepages/advocacy/autocost.htm
About the CO2 we exhale:
http://www.conspairacy.com/calculations/perperson.html
I hope this has answered your question. If not, or if any part of my
answer is unclear, please request an Answer Clarification, before
rating.
Regards, Crabcakes
Search Terms
============
Greenhouse gasses + train + bike + motocycle
CO2 exhaled
Carbon dioxide output vehicles

It doesn't matter how much carbon dioxide you exhale when you ride
your bike, because none of it contributes to the buildup of carbon
dioxide in the atmosphere. This buildup is caused by burning fossil
fuels, which releases carbon that has been bound up in the slow carbon
cycle for millions of years. All the carbon you exhale came from
plants that you ate. Or from animals or fungi you ate, but the
animals and fungi got it from plants. The plants got it from the
atmosphere. So the carbon you exhale was in the atmosphere no more
than a year or two previously, and even if you hadn't eaten it and
exhaled it, it would soon end up back in the atmosphere. Bacteria
will eat it if nothing else (it will 'rot'). The movement of carbon
through the fast carbon cycle does not change the composition of the
atmosphere. So by riding your bike you are not contributing to the
greenhouse effect at all. However, the train is also an
environmentally friendly way to get to work. Still not as good as the
bike though: Crabcakes says that you are contributing zero CO2 to the
atmosphere by riding the train, since the train would run anyway, but
I disagree. That is like saying there is no reason to vote, because
your vote won't change the outcome of the election. If more people
rode bikes, the trains could be smaller and maybe run less often, so
producing less CO2.

Forget about CO2 and consider energy. Energy usage should correlate
well with polution. Passenger trains get about 250 passenger miles per
gallon (100 to 500 depending on occupancy). This equates to about 126
kilocalories per passenger mile. Riding a bicycle at 15 miles per hour
uses about 35 kilocalories per mile of which 27 is due to cycling and
8 are from basal metabolism. This includes lots of assumptions about
weight, wind, hills, and other things, but is probably typical. So a
bicycle is almost 5 times as efficient as the train.

Hi racecar,
You said "Crabcakes says that you are contributing zero CO2 to the
atmosphere by riding the train, since the train would run anyway, but
I disagree. "
I never said that. What I said was "Keep in mind you are putting off
CO2 while ON the train too, but a bit less and you are burning less
energy sitting than pedalling a bike."
What I said was this "How much energy the train expends converting
energy to motion really seems moot in this scenario, as the train is
running whether
you are on it or not. The extra energy the train might expend if you
were on it is beyond the scope of this question! :-) However, the
number of people riding the train is surely varied day to day, so we
really don?t need to worry about the amount of energy needed if you
were on the train. The train is running daily, whether or not you are
aboard."
The paragraph comments on the amount of energy needed to move the train.

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